Circuit components



Feb. 28, 1961 J. 5. WILKERSON 2,973,497

CIRCUIT COMPONENTS Filed July 1, 1959 5 INVENTOR JOH N S. WILKERSON BY AORNEY United States Patent CIRCUIT COMPONENTS John S. Wilkerson,Clearwater, Fla., assignor to Minueapolis-Honeywell Regulator Company,Minneapolis, Minn., a corporation of Delaware Filed July 1, 1959, Ser.No. 824,331

4 Claims. (Cl. 338-143) This invention're'lates to the field ofelectrical circuit components and more especially to variable resistorsof high precision. It is the object of the invention to provide animproved variable resistor in which tracking of the movable contact withthe resistance element is smooth and free from binding or chatter, andin which wear with its attendant electrical noise is reduced.

Various other objects, advantages and features of novelty notparticularly enumerated above which characterize my invention arepointed out with particularity in the claims annexed hereto and forminga part hereof. However, for a better understanding of the invention, itsadvantages, and objects attained by its use, reference should be had tothe subjoined drawing, which forms a further part hereof, and to theaccompanying descriptive matter, in which I have illustrated anddescribed a preferred embodiment of my invention.

In the drawing Figure l is a fragmentary showing of a variable resistorconstructed according to the invention, partly in section;

Figure 2 is a showing of the slider assembly of Figure 1 looking outwardfrom the center of the winding;

Figures 3 and 4 are sections taken along the lines 3-3 and 44 of Figure2; and

Figure 5 shows a modification of the invention.

In the drawing element is a form of suitable insulating materialpreferably grooved at 11 and 12 to receive a pair of helices 13 and 14comprising respectively the resistance element and a collector elementof the variable resistor. Resistance wire 13 is preferably made of analloy known as Sigmund Cohn L.T.C. wire, and is of relatively smalldiameter, high resistivity, and excellent uniformity of resistance.Collector wire 14 is preferably made of a gold alloy known commerciallyas Ney-Oro G and is of relatively large diameter and of low resistivity.The wires are fastened to the form in any conventional fashion and arebrought out from there to the terminals of the device.

Cooperating with the resistance assembly 15 just described is a sliderassembly 16 including a central drive portion 17, a spring 20, and arelatively stiff wiper arm 21. Spring 20 is fastened to portion 17 as byrivets 22, and bears a contact pad 23 at its outer end. Wiper arm 21 isfastened to drive portion 17 as by rivets 24 and also bears a contactpad 25 at its end. Ar-m 21 is cut away at 26, and carries a pair ofwipers 27 and 30. The assembly is generally arcuate to conform to theshape of form 10. and Wipers 27 and 30 extend inwardly from the concavesurface, as do pads '23 and 25. Each of the latter is large enough toengage two adjacent turns of collector wire 14.

Extending inwardly from the central drive portion 17 is a shoe 31 havinga groove 32 proportioned to engage collector wire 14 without engagingresistance wire 13. It has been found that if pads 23 and 25, shoe 31,and wipers 27 and 30 are made of the alloy commercially known as Paliney#7 the wear resulting from rubbing between the movable and stationarycomponents is reduced to a minimum.

Drive portion 17 is cross bored at 33 to give a smooth sliding fit witha rod 34 aligned with form 10 and spaced therefrom slightly. Provisionis made for causing relative movement between form 10 and rod 33, eitherby holding the rod stationary and rotating the form about its axis, or'by holding the form stationary and mounting rod 33 on an arm forrotation about the axis of the form. Both methods are satisfactory andchoice is dictated by convenience in packaging and other considerations.

The elements of slider assembly 16 are so positioned that when groove 32engages a turn of the collector wire, wipers 27 and 30 engage anadjacent turn of the resistance wire at closely spaced intervalstherealong, and each of the pads 23 and 25 rides on a pair of adjacentturns of the collector wire. The resilience of spring 20, wiper arm 2 1,and wipers 27, 30 is such that the latter engage the resistance windingvery lightly, and since they are of very light construction the assemblyis essentially immune to vibration difficulties.

A modification of the invention is shown in Figure 5, which differs fromthe previously disclosed arrangement in that shoe 41 is not rigidlyattached to drive portion 42, but is carried in a resilient member 43connected to wiper arm 44: the other elements are the same as in thepreviously described embodiment.

Numerous objects and advantages of my invention have been set forth inthe foregoing description together with details of the structure andfunction of the invention, and the novel features thereof are pointedout in the appended claims. The disclosure, however, is illustrativeonly, and I may make changes in detail, especially in matters of shape,size, and arrangement of parts, within the principle of the invention,to the full extent indicated by the broad general meaning of the termsin which the appended claims are expressed.

I claim as my invention:

1. In combination: a cylindrical form; first and second mutually spacedhelices on said form, the first helix comprising a plurality of turns ofrelatively large diameter wire having relatively low resistivity and thesecond helix comprising a plurality of turns of relatively smalldiameter wire having relatively high resistivity, said helices havingthe same helix angle so that the turns of one helix lie between theturns of the other helix; means making electrical connection to saidhelices; a resilient, electrically conductive slider assembly comprisinga central drive portion, a pair of end bearing portions, andintermediate wiper means, said slider assembly being generally arcuateto conform to the shape of said cylinder; and means mounting saidassembly for movement parallel to the axis of said form and spacedtherefrom, said drive portion comprising a shoe engaging a turn of saidfirst helix without engaging either of the adjacent turns of said secondhelix so that said assembly is moved axially of said form upon relativerotation between said form and the mounting means, said bearing portionseach comprising a pad proportioned to contact a pair of adjacent turnsof said first helix, and said wiper means comprising a pair of resilientcontacts engaging a turn of said second helix at closely spaced pointstherealong, so that regardless of the sense of said relative rotationone of said contacts can remove unwanted material from said second helixto insure good electric contact thereof with the other contact.

2. In combination: a plurality of spaced, aligned wires, comprising apair of electrically connected wires of relatively large diameter andrelatively low resistivity and a further wire therebetween of relativelysmall diameter and relatively high resistivity; a slider assemblycomprising a central drive portion including a shoe engaging at leastone of the wires of said pair, a pair of resilient end bearing portionseach including a conductive pad contacting said pair of wires, and wipermeans comprising a pair of contacts electrically connected to at leastone of said pads and engaging said second wire at closely spaced pointstherealong; mounting means slidably engaging said drive portion toprevent motion of said slider assembly with respect to said wires exceptin the direction of said wires, and means causing relative motion,between said wires and said mounting means, having a component alignedwith the direction of said wires.

3. In combination: a plurality of spaced, aligned wires comprising apair of electrically connected wires of relatively large diameter andrelatively low resistivity and a further wire therebetween of relativelysmall diameter and relatively high resistivity; an arcuate sliderassembly comprising a central drive portion including a shoe engaging atleast one of the wires of said pair, a pair of resilient end bearingportions each including a conductive pad contacting said pair of Wires,and wiper means comprising a pair of contacts electrically connected toat least one of said pads and engaging said second wire at closelyspaced points therealong; mounting means slidably engag ing said driveportion to prevent motion of said slider assembly, with respect to saidwires, except in the direction of said wires; and means causing relativemotion, between said wires and said mounting means having a componentaligned with the direction of said wires.

4. In combination: a collector wire; a resistance wire aligned with saidcollector wire, and a movable slider assembly bridging between saidwires; said slider assembly comprising a pair of wipers makingelectrical contact with said resistance wire at closely spaced pointstherealong, a pad connected to said wipers and making electrical contactwith said collector wire, and a shoe mechanically engaging saidcollector wire so as to guide the movement of said slider assembly inalignment with said wires.

References Cited in the file of this patent UNITED STATES PATENTS

